<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        html {
            font-size: 12px;
        }
        div {
            font-size: 10px;
            width: 20rem;
            height: 20rem;
            background-color: pink;
        }
        p {
            width: 10rem;
            height: 10rem;
            background-color: blue;
        }
    </style>
</head>
<body>
    <div>
        <p></p>
    </div>
</body>
</html>